these exam questions cover a range of environmental pollution, specifically on microplastics within the environment.
there are questions on the definitions of various environmental pollution phrases, as well as larger questions on explaining the adverse effects on environmnetal pollutants.
...
i. Explain why it has proven difficult for the scientific community to agree a definition for the
term “microplastics.”
The term microplastics refers to all plastic particles which are smaller than 5mm. This definition
was difficult to agree on due to the arguments that the definition should be in SI units (which are
metres, and not millimetres), and that the term ‘micro’ should only be used with particles of
micrometre size.
ii. Explain the difference between macro-, meso- and microplastics.
The differences are the sizes of the defined plastics. Macroplastics are classed as debris which is
larger than 25mm. Mesoplastics are particles which are in the range of 5-25mm, and
microplastics are particles that are smaller than 5mm in size.
iii. Briefly discuss methods by which micro-plastics may be removed from the oceans.
There are 3 main ways to remove plastics from the ocean: drone use, booms or collection
devices, and vessels. However, for microplastics, the removal via vessels is not effective and
therefore not necessary. Drone uses have autonomous control and operation to suck the water
up through filters. This leaves the remaining plastic trapped in the filters. They can be functioned
by either solar power or battery use.
This method is effective, however due to battery use and operation, it has a high cost and
limited capacity to operate. Furthermore, due to the drones being small in size, it will take too
long to remove all microplastics needed with this method.
Booms are collection devices are capable of capturing floating litter in rivers and oceans. The
currents trap the litter and microplastics in the traps. This is beneficial; however, it requires high
maintenance to empty the traps. It can also be questioned as to how many microplastics get
caught in these, as microplastics which are very small in size will not get caught in the nets.
However, by using fine mesh nets, they are more likely to get removed with this method. The
Ocean Clean Up Project is an example of this removal method.
Section A.2:
Define ALL of the following terms with respect to water pollution:
, i. Alien invasive species
When an organism that is not native to a water body is introduced (by accident or deliberate
cause) and establishes in the habitat, which threatens native biological diversity, by negatively
effecting the economy and environment, as well as human harm. An example of an invasive
species is the Nile Perch in Lake Victoria, which caused 200 species to become extinct in the
1980’s.
i. Endocrine disruptor
Endocrine disruptors mimic or block chemicals which are naturally found in the body, as well as
entering hormonal levels in relation to the endocrine system. Microplastics are assumed to act
as an endocrine disruptor.
ii. Grit removal in wastewater treatment
Grit removal is one of three steps present in the preliminary treatment in sewage treatment. It is
a flotation process meaning the steps involve separating solid particles from the liquid. The
sewage/wastewater travels through a sand or grit channel chamber which alters in velocity,
causing the settling of solid particles- and hence separating the solid and water. This reduces
BOD (Biological Oxygen Demand) which is the amount of oxygen consumed by microorganisms
as they decompose organic matter.
iii. Detergent
Detergents are part of the domestic wastewaters. They are surfactants, or a mixture of such,
with cleaning properties in a dilute solution. Detergents are similar to soap; however, they are
more soluble in hard water, due to the polar sulfonate groups preferably not binding with
calcium and other ions present in hardwater. Detergents are amphiphilic, meaning part
hydrophilic (water-liking) and part hydrophobic (water-hating, or non-polar).
iv. Electrical conductivity
Electrical conductivity is one of the 3 general indicators for water quality. This is the ability of a
water body to carry an electrical current, which is measured in Siemens (µS cm^-1) which varies
depending on the level of mineralisation in the water. The electrical resistant measures the
opposition to the passage of electric current, like friction. The electrical conductivity is
dependent on the number of anions and cations present in the water. Cl- are negatively charged
anions which will cause ionic bonds in the water with the cations, such as K+. This leads to an
imbalance of charges and ions are produced- and these ions can move freely in the water and
hence can carry an electrical conductivity. The more metals, the more anions and cations to
produce these ions.
Section A.3:
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